1. Field of the Invention
The present invention relates to a variable capacitance element and a variable capacitance device, and in particular, to a variable capacitance element that changes an opposite distance between capacitive electrodes using an electrostatic force generated by application of a driving voltage and a variable capacitance device having the variable capacitance element.
2. Description of the Related Art
In general, a variable capacitance element is provided as a variable-capacitance capacitor in an electronic circuit, such as an oscillation circuit and a modulation circuit, in order to change an electrostatic capacitance such that a desired output can be obtained in the electronic circuit. For example, when the variable capacitance element is used in an MEMS, the electrostatic capacitance between electrodes is changed by forming the variable capacitance element in a three-dimensional shape so that the opposite distance between the electrodes can be freely changed.
An example of a known variable capacitance element 102 is shown in FIGS. 21 and 22. The known variable capacitance element 102 includes a supporting substrate 105, a cantilever 104, a fixed electrode 107, and a movable electrode 106, as shown in FIGS. 21 and 22. The cantilever 104 is formed in a crank shape, and an end 104a of the cantilever 104 is fixed as a supporting end on a surface of the supporting substrate 105. Furthermore, the plate-shaped movable electrode 106 is disposed on a surface of the cantilever 104 opposite the supporting substrate 105, and the plate-shaped fixed electrode 107 is disposed on a surface of the supporting substrate 105 opposite the movable electrode 106. The widths of the cantilever 104 and the movable electrode 106 are decreased toward the front end side from the supporting end side. In addition, when a driving voltage is applied between the fixed electrode 107 and the movable electrode 106, an electrostatic force is generated between the fixed electrode 107, and as a result, the movable electrode 106 and the cantilever 104 is deflected toward the supporting substrate 105 side. Thus, since the opposite distance between the fixed electrode 107 and the movable electrode 106 is increased or decreased by changing a driving voltage to adjust the electrostatic force, the electrostatic capacitance between the fixed electrode 107 and the movable electrode 106 is changed.
However, in order to increase the electrostatic capacitance between the movable electrode 106 and the fixed electrode 107 in the known variable capacitance element 102, a large driving voltage for increasing the amount of deflection of the cantilever 104 needs to be applied to make the distance between the movable electrode 106 and the fixed electrode 107 small and the state should be maintained. For this reason, it is necessary to continuously apply a large driving voltage in order to obtain a large electrostatic capacitance. As a result, a problem occurs that the power consumption of the variable capacitance element 102 and a variable capacitance device increases.